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Aalto’s new community-built sauna floats on repurposed wind turbine blades

Published: 18.11.2024

Made from tough fibreglass, wind turbine blades are notoriously difficult to recycle. Now, Reverlast, a company founded by Aalto University alumni, is transforming them into durable floating structures designed to withstand even harsh marine conditions. The company’s first project is Aalto University’s new community sauna, which will be ready for testing just in time for the holidays.

Aerial view of a seaside pier with a floating sauna, small boat docked nearby, and grassy shore with trees. — If everything goes as planned, regular sauna activities will begin next spring.

A wind turbine generates electricity for about a quarter of a century. After that, it must be dismantled, and its parts recycled.

The metals in the turbine's tower and motor—aluminium, steel, copper, and lead—are almost entirely recyclable, with recovery rates nearing 100%. However, repurposing the fibreglass from the blades is more challenging.

Burying blades has long been banned in Finland, and an EU directive will enforce this prohibition across Europe starting next year. Currently, the most common solution is to crush decommissioned blades for use as fuel and raw material in cement production. While using recycled material reduces emissions from cement manufacturing, the crushing process is energy-intensive, and burning the material produces carbon dioxide.

Three people are standing inside a large, hollow fiberglass wing. — The massive blades are secured to the wind turbine rotor with sturdy bolts. Pictured from left: Reverlast's design lead Henrik Jansson, Aalto Sustainability Club Chair Martina Presepi, and Reverlast co-founder Ossi Heiskala.

There are better solutions, says Ossi Heiskala, an alum of Aalto University's School of Business and co-founder of the company Reverlast.

‘We repurpose turbine blades to build floating docks and pontoon structures,’ he explains. ‘This reduces the need for traditional pontoon materials like concrete and polyethylene plastic, making the solution even more environmentally friendly. Our prototype dock prevents roughly 2.6 tons of carbon dioxide emissions, and the larger and more numerous the docks we build, the greater the impact’.

An idea born at sea

The company's co-founder and CEO, Johannes Peace, who studied bio- and chemical engineering as well as international design business management at Aalto University, is an avid sailor. Three years ago, he began to recognise that wind turbine blades are made from the same fine material as boats, designed to withstand harsh marine conditions for decades.

Two people are examining large pontoons — The pontoons of the prototype dock are filled with polystyrene. In the future, the cutting surfaces will be sealed with a tight cover, eliminating the need for foam filling. The cutting was done by Lapa Recycling, Reverlast's partner.

Peace approached Heiskala to explore the possibility of developing a business based on the idea. The decision was an easy one. ‘A positive environmental impact combined with a business opportunity—of course, I was on board,’ Heiskala says with a smile.

After thorough groundwork, the team was accepted into the Kiuas accelerator program last spring, and the company was founded in August.

Reverlast’s first project is Aalto University’s new community sauna. The sauna itself is a traditional wood-heated barrel sauna, assembled from a pre-made kit. But instead of being placed on land, it will be installed on a dock that floats on pontoons made from four wind turbine blades. The pontoons are filled with polystyrene, and each weighs over 300 kilograms.

The dock is more stable than a traditional floating pontoon dock and extremely durable. The fibreglass layer in the blade sections used for the pontoons is up to 6 centimetres thick—far more robust than the 1-centimetre layer typical in sailboats.

‘The pontoon is incredibly strong—it won’t break, that’s for sure. Our job is to design the other parts to ensure they’ll last for decades as well,’ says Heiskala.

The power of community

Finland’s wind turbine fleet is still young, which is why only a small number are dismantled each year—around ten to twenty, according to Heiskala’s estimate.

In the next decade, the pace will pick up, increasing the demand for better circular solutions that benefit both the environment and turbine owners.

The dock pontoons were cut from the midsection of the blade. The narrow tip of the blade, in turn, could be used for lighter structures, such as swimming platforms, Heiskala envisions.

‘We’re starting with floating docks because our team has a lot of expertise in that area. However, we already have more ambitious plans—the sturdier sections of the blades could be used for larger structures, like breakwaters,’ he explains.

An aerial view of a large building by the water, with boats at the dock and a wind turbine blade in the water serving as a breakwater. — An image of a breakwater made from a wind turbine blade.

The community sauna promoting sustainability has received an enthusiastic response and support from multiple sources. Aalto University has awarded Sustainability Action Booster funding for the material costs, and a group of eager students has volunteered to help with construction.

Once the sauna is completed, the Polytechnical Sauna Society and the Aalto Sustainability Club will jointly oversee its operation and development.

If all goes as planned, testing will take place before Christmas, and the sauna is expected to open to the entire Aalto community next spring. The team believes it will become a relaxed gathering place that fosters community, especially among students, attracting thousands of visitors annually.

Martina Presepi, Chair of the Aalto Sustainability Club, is eagerly awaiting its completion.

‘I love sauna, and since moving to Finland, I’ve gone every week. Otaniemi has many saunas, but this will be the first with direct access to the water. It’s been a joy to spread the word about such a creative, ambitious, and sustainable project.’